Add initial gamepad support.

Change-Id: I0439648f6eb5405f200e4223c915eb3a418b32b9

1 files changed, 729 insertions, 0 deletions

diff --git a/libs/ui/InputDevice.cpp b/libs/ui/InputDevice.cpp
new file mode 100644
index 0000000000..6014017239
--- /dev/null
+++ b/libs/ui/InputDevice.cpp
@@ -0,0 +1,729 @@
+//
+// Copyright 2010 The Android Open Source Project
+//
+// The input reader.
+//
+#define LOG_TAG "InputDevice"
+
+//#define LOG_NDEBUG 0
+
+// Log debug messages for each raw event received from the EventHub.
+#define DEBUG_RAW_EVENTS 0
+
+// Log debug messages about touch screen filtering hacks.
+#define DEBUG_HACKS 0
+
+// Log debug messages about virtual key processing.
+#define DEBUG_VIRTUAL_KEYS 0
+
+// Log debug messages about pointers.
+#define DEBUG_POINTERS 0
+
+// Log debug messages about pointer assignment calculations.
+#define DEBUG_POINTER_ASSIGNMENT 0
+
+#include <cutils/log.h>
+#include <ui/InputDevice.h>
+
+#include <stddef.h>
+#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
+
+/* Slop distance for jumpy pointer detection.
+ * The vertical range of the screen divided by this is our epsilon value. */
+#define JUMPY_EPSILON_DIVISOR 212
+
+/* Number of jumpy points to drop for touchscreens that need it. */
+#define JUMPY_TRANSITION_DROPS 3
+#define JUMPY_DROP_LIMIT 3
+
+/* Maximum squared distance for averaging.
+ * If moving farther than this, turn of averaging to avoid lag in response. */
+#define AVERAGING_DISTANCE_LIMIT (75 * 75)
+
+
+namespace android {
+
+// --- Static Functions ---
+
+template<typename T>
+inline static T abs(const T& value) {
+    return value < 0 ? - value : value;
+}
+
+template<typename T>
+inline static T min(const T& a, const T& b) {
+    return a < b ? a : b;
+}
+
+template<typename T>
+inline static void swap(T& a, T& b) {
+    T temp = a;
+    a = b;
+    b = temp;
+}
+
+
+// --- InputDevice ---
+
+InputDevice::InputDevice(int32_t id, uint32_t classes, String8 name) :
+    id(id), classes(classes), name(name), ignored(false) {
+}
+
+void InputDevice::reset() {
+    if (isKeyboard()) {
+        keyboard.reset();
+    }
+
+    if (isTrackball()) {
+        trackball.reset();
+    }
+
+    if (isMultiTouchScreen()) {
+        multiTouchScreen.reset();
+    } else if (isSingleTouchScreen()) {
+        singleTouchScreen.reset();
+    }
+
+    if (isTouchScreen()) {
+        touchScreen.reset();
+    }
+}
+
+
+// --- InputDevice::TouchData ---
+
+void InputDevice::TouchData::copyFrom(const TouchData& other) {
+    pointerCount = other.pointerCount;
+    idBits = other.idBits;
+
+    for (uint32_t i = 0; i < pointerCount; i++) {
+        pointers[i] = other.pointers[i];
+        idToIndex[i] = other.idToIndex[i];
+    }
+}
+
+
+// --- InputDevice::KeyboardState ---
+
+void InputDevice::KeyboardState::reset() {
+    current.metaState = META_NONE;
+    current.downTime = 0;
+}
+
+
+// --- InputDevice::TrackballState ---
+
+void InputDevice::TrackballState::reset() {
+    accumulator.clear();
+    current.down = false;
+    current.downTime = 0;
+}
+
+
+// --- InputDevice::TouchScreenState ---
+
+void InputDevice::TouchScreenState::reset() {
+    lastTouch.clear();
+    downTime = 0;
+    currentVirtualKey.status = CurrentVirtualKeyState::STATUS_UP;
+
+    for (uint32_t i = 0; i < MAX_POINTERS; i++) {
+        averagingTouchFilter.historyStart[i] = 0;
+        averagingTouchFilter.historyEnd[i] = 0;
+    }
+
+    jumpyTouchFilter.jumpyPointsDropped = 0;
+}
+
+struct PointerDistanceHeapElement {
+    uint32_t currentPointerIndex : 8;
+    uint32_t lastPointerIndex : 8;
+    uint64_t distance : 48; // squared distance
+};
+
+void InputDevice::TouchScreenState::calculatePointerIds() {
+    uint32_t currentPointerCount = currentTouch.pointerCount;
+    uint32_t lastPointerCount = lastTouch.pointerCount;
+
+    if (currentPointerCount == 0) {
+        // No pointers to assign.
+        currentTouch.idBits.clear();
+    } else if (lastPointerCount == 0) {
+        // All pointers are new.
+        currentTouch.idBits.clear();
+        for (uint32_t i = 0; i < currentPointerCount; i++) {
+            currentTouch.pointers[i].id = i;
+            currentTouch.idToIndex[i] = i;
+            currentTouch.idBits.markBit(i);
+        }
+    } else if (currentPointerCount == 1 && lastPointerCount == 1) {
+        // Only one pointer and no change in count so it must have the same id as before.
+        uint32_t id = lastTouch.pointers[0].id;
+        currentTouch.pointers[0].id = id;
+        currentTouch.idToIndex[id] = 0;
+        currentTouch.idBits.value = BitSet32::valueForBit(id);
+    } else {
+        // General case.
+        // We build a heap of squared euclidean distances between current and last pointers
+        // associated with the current and last pointer indices.  Then, we find the best
+        // match (by distance) for each current pointer.
+        PointerDistanceHeapElement heap[MAX_POINTERS * MAX_POINTERS];
+
+        uint32_t heapSize = 0;
+        for (uint32_t currentPointerIndex = 0; currentPointerIndex < currentPointerCount;
+                currentPointerIndex++) {
+            for (uint32_t lastPointerIndex = 0; lastPointerIndex < lastPointerCount;
+                    lastPointerIndex++) {
+                int64_t deltaX = currentTouch.pointers[currentPointerIndex].x
+                        - lastTouch.pointers[lastPointerIndex].x;
+                int64_t deltaY = currentTouch.pointers[currentPointerIndex].y
+                        - lastTouch.pointers[lastPointerIndex].y;
+
+                uint64_t distance = uint64_t(deltaX * deltaX + deltaY * deltaY);
+
+                // Insert new element into the heap (sift up).
+                heap[heapSize].currentPointerIndex = currentPointerIndex;
+                heap[heapSize].lastPointerIndex = lastPointerIndex;
+                heap[heapSize].distance = distance;
+                heapSize += 1;
+            }
+        }
+
+        // Heapify
+        for (uint32_t startIndex = heapSize / 2; startIndex != 0; ) {
+            startIndex -= 1;
+            for (uint32_t parentIndex = startIndex; ;) {
+                uint32_t childIndex = parentIndex * 2 + 1;
+                if (childIndex >= heapSize) {
+                    break;
+                }
+
+                if (childIndex + 1 < heapSize
+                        && heap[childIndex + 1].distance < heap[childIndex].distance) {
+                    childIndex += 1;
+                }
+
+                if (heap[parentIndex].distance <= heap[childIndex].distance) {
+                    break;
+                }
+
+                swap(heap[parentIndex], heap[childIndex]);
+                parentIndex = childIndex;
+            }
+        }
+
+#if DEBUG_POINTER_ASSIGNMENT
+        LOGD("calculatePointerIds - initial distance min-heap: size=%d", heapSize);
+        for (size_t i = 0; i < heapSize; i++) {
+            LOGD("  heap[%d]: cur=%d, last=%d, distance=%lld",
+                    i, heap[i].currentPointerIndex, heap[i].lastPointerIndex,
+                    heap[i].distance);
+        }
+#endif
+
+        // Pull matches out by increasing order of distance.
+        // To avoid reassigning pointers that have already been matched, the loop keeps track
+        // of which last and current pointers have been matched using the matchedXXXBits variables.
+        // It also tracks the used pointer id bits.
+        BitSet32 matchedLastBits(0);
+        BitSet32 matchedCurrentBits(0);
+        BitSet32 usedIdBits(0);
+        bool first = true;
+        for (uint32_t i = min(currentPointerCount, lastPointerCount); i > 0; i--) {
+            for (;;) {
+                if (first) {
+                    // The first time through the loop, we just consume the root element of
+                    // the heap (the one with smallest distance).
+                    first = false;
+                } else {
+                    // Previous iterations consumed the root element of the heap.
+                    // Pop root element off of the heap (sift down).
+                    heapSize -= 1;
+                    assert(heapSize > 0);
+
+                    // Sift down.
+                    heap[0] = heap[heapSize];
+                    for (uint32_t parentIndex = 0; ;) {
+                        uint32_t childIndex = parentIndex * 2 + 1;
+                        if (childIndex >= heapSize) {
+                            break;
+                        }
+
+                        if (childIndex + 1 < heapSize
+                                && heap[childIndex + 1].distance < heap[childIndex].distance) {
+                            childIndex += 1;
+                        }
+
+                        if (heap[parentIndex].distance <= heap[childIndex].distance) {
+                            break;
+                        }
+
+                        swap(heap[parentIndex], heap[childIndex]);
+                        parentIndex = childIndex;
+                    }
+
+#if DEBUG_POINTER_ASSIGNMENT
+                    LOGD("calculatePointerIds - reduced distance min-heap: size=%d", heapSize);
+                    for (size_t i = 0; i < heapSize; i++) {
+                        LOGD("  heap[%d]: cur=%d, last=%d, distance=%lld",
+                                i, heap[i].currentPointerIndex, heap[i].lastPointerIndex,
+                                heap[i].distance);
+                    }
+#endif
+                }
+
+                uint32_t currentPointerIndex = heap[0].currentPointerIndex;
+                if (matchedCurrentBits.hasBit(currentPointerIndex)) continue; // already matched
+
+                uint32_t lastPointerIndex = heap[0].lastPointerIndex;
+                if (matchedLastBits.hasBit(lastPointerIndex)) continue; // already matched
+
+                matchedCurrentBits.markBit(currentPointerIndex);
+                matchedLastBits.markBit(lastPointerIndex);
+
+                uint32_t id = lastTouch.pointers[lastPointerIndex].id;
+                currentTouch.pointers[currentPointerIndex].id = id;
+                currentTouch.idToIndex[id] = currentPointerIndex;
+                usedIdBits.markBit(id);
+
+#if DEBUG_POINTER_ASSIGNMENT
+                LOGD("calculatePointerIds - matched: cur=%d, last=%d, id=%d, distance=%lld",
+                        lastPointerIndex, currentPointerIndex, id, heap[0].distance);
+#endif
+                break;
+            }
+        }
+
+        // Assign fresh ids to new pointers.
+        if (currentPointerCount > lastPointerCount) {
+            for (uint32_t i = currentPointerCount - lastPointerCount; ;) {
+                uint32_t currentPointerIndex = matchedCurrentBits.firstUnmarkedBit();
+                uint32_t id = usedIdBits.firstUnmarkedBit();
+
+                currentTouch.pointers[currentPointerIndex].id = id;
+                currentTouch.idToIndex[id] = currentPointerIndex;
+                usedIdBits.markBit(id);
+
+#if DEBUG_POINTER_ASSIGNMENT
+                LOGD("calculatePointerIds - assigned: cur=%d, id=%d",
+                        currentPointerIndex, id);
+#endif
+
+                if (--i == 0) break; // done
+                matchedCurrentBits.markBit(currentPointerIndex);
+            }
+        }
+
+        // Fix id bits.
+        currentTouch.idBits = usedIdBits;
+    }
+}
+
+/* Special hack for devices that have bad screen data: if one of the
+ * points has moved more than a screen height from the last position,
+ * then drop it. */
+bool InputDevice::TouchScreenState::applyBadTouchFilter() {
+    // This hack requires valid axis parameters.
+    if (! parameters.yAxis.valid) {
+        return false;
+    }
+
+    uint32_t pointerCount = currentTouch.pointerCount;
+
+    // Nothing to do if there are no points.
+    if (pointerCount == 0) {
+        return false;
+    }
+
+    // Don't do anything if a finger is going down or up.  We run
+    // here before assigning pointer IDs, so there isn't a good
+    // way to do per-finger matching.
+    if (pointerCount != lastTouch.pointerCount) {
+        return false;
+    }
+
+    // We consider a single movement across more than a 7/16 of
+    // the long size of the screen to be bad.  This was a magic value
+    // determined by looking at the maximum distance it is feasible
+    // to actually move in one sample.
+    int32_t maxDeltaY = parameters.yAxis.range * 7 / 16;
+
+    // XXX The original code in InputDevice.java included commented out
+    //     code for testing the X axis.  Note that when we drop a point
+    //     we don't actually restore the old X either.  Strange.
+    //     The old code also tries to track when bad points were previously
+    //     detected but it turns out that due to the placement of a "break"
+    //     at the end of the loop, we never set mDroppedBadPoint to true
+    //     so it is effectively dead code.
+    // Need to figure out if the old code is busted or just overcomplicated
+    // but working as intended.
+
+    // Look through all new points and see if any are farther than
+    // acceptable from all previous points.
+    for (uint32_t i = pointerCount; i-- > 0; ) {
+        int32_t y = currentTouch.pointers[i].y;
+        int32_t closestY = INT_MAX;
+        int32_t closestDeltaY = 0;
+
+#if DEBUG_HACKS
+        LOGD("BadTouchFilter: Looking at next point #%d: y=%d", i, y);
+#endif
+
+        for (uint32_t j = pointerCount; j-- > 0; ) {
+            int32_t lastY = lastTouch.pointers[j].y;
+            int32_t deltaY = abs(y - lastY);
+
+#if DEBUG_HACKS
+            LOGD("BadTouchFilter: Comparing with last point #%d: y=%d deltaY=%d",
+                    j, lastY, deltaY);
+#endif
+
+            if (deltaY < maxDeltaY) {
+                goto SkipSufficientlyClosePoint;
+            }
+            if (deltaY < closestDeltaY) {
+                closestDeltaY = deltaY;
+                closestY = lastY;
+            }
+        }
+
+        // Must not have found a close enough match.
+#if DEBUG_HACKS
+        LOGD("BadTouchFilter: Dropping bad point #%d: newY=%d oldY=%d deltaY=%d maxDeltaY=%d",
+                i, y, closestY, closestDeltaY, maxDeltaY);
+#endif
+
+        currentTouch.pointers[i].y = closestY;
+        return true; // XXX original code only corrects one point
+
+    SkipSufficientlyClosePoint: ;
+    }
+
+    // No change.
+    return false;
+}
+
+/* Special hack for devices that have bad screen data: drop points where
+ * the coordinate value for one axis has jumped to the other pointer's location.
+ */
+bool InputDevice::TouchScreenState::applyJumpyTouchFilter() {
+    // This hack requires valid axis parameters.
+    if (! parameters.yAxis.valid) {
+        return false;
+    }
+
+    uint32_t pointerCount = currentTouch.pointerCount;
+    if (lastTouch.pointerCount != pointerCount) {
+#if DEBUG_HACKS
+        LOGD("JumpyTouchFilter: Different pointer count %d -> %d",
+                lastTouch.pointerCount, pointerCount);
+        for (uint32_t i = 0; i < pointerCount; i++) {
+            LOGD("  Pointer %d (%d, %d)", i,
+                    currentTouch.pointers[i].x, currentTouch.pointers[i].y);
+        }
+#endif
+
+        if (jumpyTouchFilter.jumpyPointsDropped < JUMPY_TRANSITION_DROPS) {
+            if (lastTouch.pointerCount == 1 && pointerCount == 2) {
+                // Just drop the first few events going from 1 to 2 pointers.
+                // They're bad often enough that they're not worth considering.
+                currentTouch.pointerCount = 1;
+                jumpyTouchFilter.jumpyPointsDropped += 1;
+
+#if DEBUG_HACKS
+                LOGD("JumpyTouchFilter: Pointer 2 dropped");
+#endif
+                return true;
+            } else if (lastTouch.pointerCount == 2 && pointerCount == 1) {
+                // The event when we go from 2 -> 1 tends to be messed up too
+                currentTouch.pointerCount = 2;
+                currentTouch.pointers[0] = lastTouch.pointers[0];
+                currentTouch.pointers[1] = lastTouch.pointers[1];
+                jumpyTouchFilter.jumpyPointsDropped += 1;
+
+#if DEBUG_HACKS
+                for (int32_t i = 0; i < 2; i++) {
+                    LOGD("JumpyTouchFilter: Pointer %d replaced (%d, %d)", i,
+                            currentTouch.pointers[i].x, currentTouch.pointers[i].y);
+                }
+#endif
+                return true;
+            }
+        }
+        // Reset jumpy points dropped on other transitions or if limit exceeded.
+        jumpyTouchFilter.jumpyPointsDropped = 0;
+
+#if DEBUG_HACKS
+        LOGD("JumpyTouchFilter: Transition - drop limit reset");
+#endif
+        return false;
+    }
+
+    // We have the same number of pointers as last time.
+    // A 'jumpy' point is one where the coordinate value for one axis
+    // has jumped to the other pointer's location. No need to do anything
+    // else if we only have one pointer.
+    if (pointerCount < 2) {
+        return false;
+    }
+
+    if (jumpyTouchFilter.jumpyPointsDropped < JUMPY_DROP_LIMIT) {
+        int jumpyEpsilon = parameters.yAxis.range / JUMPY_EPSILON_DIVISOR;
+
+        // We only replace the single worst jumpy point as characterized by pointer distance
+        // in a single axis.
+        int32_t badPointerIndex = -1;
+        int32_t badPointerReplacementIndex = -1;
+        int32_t badPointerDistance = INT_MIN; // distance to be corrected
+
+        for (uint32_t i = pointerCount; i-- > 0; ) {
+            int32_t x = currentTouch.pointers[i].x;
+            int32_t y = currentTouch.pointers[i].y;
+
+#if DEBUG_HACKS
+            LOGD("JumpyTouchFilter: Point %d (%d, %d)", i, x, y);
+#endif
+
+            // Check if a touch point is too close to another's coordinates
+            bool dropX = false, dropY = false;
+            for (uint32_t j = 0; j < pointerCount; j++) {
+                if (i == j) {
+                    continue;
+                }
+
+                if (abs(x - currentTouch.pointers[j].x) <= jumpyEpsilon) {
+                    dropX = true;
+                    break;
+                }
+
+                if (abs(y - currentTouch.pointers[j].y) <= jumpyEpsilon) {
+                    dropY = true;
+                    break;
+                }
+            }
+            if (! dropX && ! dropY) {
+                continue; // not jumpy
+            }
+
+            // Find a replacement candidate by comparing with older points on the
+            // complementary (non-jumpy) axis.
+            int32_t distance = INT_MIN; // distance to be corrected
+            int32_t replacementIndex = -1;
+
+            if (dropX) {
+                // X looks too close.  Find an older replacement point with a close Y.
+                int32_t smallestDeltaY = INT_MAX;
+                for (uint32_t j = 0; j < pointerCount; j++) {
+                    int32_t deltaY = abs(y - lastTouch.pointers[j].y);
+                    if (deltaY < smallestDeltaY) {
+                        smallestDeltaY = deltaY;
+                        replacementIndex = j;
+                    }
+                }
+                distance = abs(x - lastTouch.pointers[replacementIndex].x);
+            } else {
+                // Y looks too close.  Find an older replacement point with a close X.
+                int32_t smallestDeltaX = INT_MAX;
+                for (uint32_t j = 0; j < pointerCount; j++) {
+                    int32_t deltaX = abs(x - lastTouch.pointers[j].x);
+                    if (deltaX < smallestDeltaX) {
+                        smallestDeltaX = deltaX;
+                        replacementIndex = j;
+                    }
+                }
+                distance = abs(y - lastTouch.pointers[replacementIndex].y);
+            }
+
+            // If replacing this pointer would correct a worse error than the previous ones
+            // considered, then use this replacement instead.
+            if (distance > badPointerDistance) {
+                badPointerIndex = i;
+                badPointerReplacementIndex = replacementIndex;
+                badPointerDistance = distance;
+            }
+        }
+
+        // Correct the jumpy pointer if one was found.
+        if (badPointerIndex >= 0) {
+#if DEBUG_HACKS
+            LOGD("JumpyTouchFilter: Replacing bad pointer %d with (%d, %d)",
+                    badPointerIndex,
+                    lastTouch.pointers[badPointerReplacementIndex].x,
+                    lastTouch.pointers[badPointerReplacementIndex].y);
+#endif
+
+            currentTouch.pointers[badPointerIndex].x =
+                    lastTouch.pointers[badPointerReplacementIndex].x;
+            currentTouch.pointers[badPointerIndex].y =
+                    lastTouch.pointers[badPointerReplacementIndex].y;
+            jumpyTouchFilter.jumpyPointsDropped += 1;
+            return true;
+        }
+    }
+
+    jumpyTouchFilter.jumpyPointsDropped = 0;
+    return false;
+}
+
+/* Special hack for devices that have bad screen data: aggregate and
+ * compute averages of the coordinate data, to reduce the amount of
+ * jitter seen by applications. */
+void InputDevice::TouchScreenState::applyAveragingTouchFilter() {
+    for (uint32_t currentIndex = 0; currentIndex < currentTouch.pointerCount; currentIndex++) {
+        uint32_t id = currentTouch.pointers[currentIndex].id;
+        int32_t x = currentTouch.pointers[currentIndex].x;
+        int32_t y = currentTouch.pointers[currentIndex].y;
+        int32_t pressure = currentTouch.pointers[currentIndex].pressure;
+
+        if (lastTouch.idBits.hasBit(id)) {
+            // Pointer was down before and is still down now.
+            // Compute average over history trace.
+            uint32_t start = averagingTouchFilter.historyStart[id];
+            uint32_t end = averagingTouchFilter.historyEnd[id];
+
+            int64_t deltaX = x - averagingTouchFilter.historyData[end].pointers[id].x;
+            int64_t deltaY = y - averagingTouchFilter.historyData[end].pointers[id].y;
+            uint64_t distance = uint64_t(deltaX * deltaX + deltaY * deltaY);
+
+#if DEBUG_HACKS
+            LOGD("AveragingTouchFilter: Pointer id %d - Distance from last sample: %lld",
+                    id, distance);
+#endif
+
+            if (distance < AVERAGING_DISTANCE_LIMIT) {
+                // Increment end index in preparation for recording new historical data.
+                end += 1;
+                if (end > AVERAGING_HISTORY_SIZE) {
+                    end = 0;
+                }
+
+                // If the end index has looped back to the start index then we have filled
+                // the historical trace up to the desired size so we drop the historical
+                // data at the start of the trace.
+                if (end == start) {
+                    start += 1;
+                    if (start > AVERAGING_HISTORY_SIZE) {
+                        start = 0;
+                    }
+                }
+
+                // Add the raw data to the historical trace.
+                averagingTouchFilter.historyStart[id] = start;
+                averagingTouchFilter.historyEnd[id] = end;
+                averagingTouchFilter.historyData[end].pointers[id].x = x;
+                averagingTouchFilter.historyData[end].pointers[id].y = y;
+                averagingTouchFilter.historyData[end].pointers[id].pressure = pressure;
+
+                // Average over all historical positions in the trace by total pressure.
+                int32_t averagedX = 0;
+                int32_t averagedY = 0;
+                int32_t totalPressure = 0;
+                for (;;) {
+                    int32_t historicalX = averagingTouchFilter.historyData[start].pointers[id].x;
+                    int32_t historicalY = averagingTouchFilter.historyData[start].pointers[id].y;
+                    int32_t historicalPressure = averagingTouchFilter.historyData[start]
+                            .pointers[id].pressure;
+
+                    averagedX += historicalX * historicalPressure;
+                    averagedY += historicalY * historicalPressure;
+                    totalPressure += historicalPressure;
+
+                    if (start == end) {
+                        break;
+                    }
+
+                    start += 1;
+                    if (start > AVERAGING_HISTORY_SIZE) {
+                        start = 0;
+                    }
+                }
+
+                averagedX /= totalPressure;
+                averagedY /= totalPressure;
+
+#if DEBUG_HACKS
+                LOGD("AveragingTouchFilter: Pointer id %d - "
+                        "totalPressure=%d, averagedX=%d, averagedY=%d", id, totalPressure,
+                        averagedX, averagedY);
+#endif
+
+                currentTouch.pointers[currentIndex].x = averagedX;
+                currentTouch.pointers[currentIndex].y = averagedY;
+            } else {
+#if DEBUG_HACKS
+                LOGD("AveragingTouchFilter: Pointer id %d - Exceeded max distance", id);
+#endif
+            }
+        } else {
+#if DEBUG_HACKS
+            LOGD("AveragingTouchFilter: Pointer id %d - Pointer went up", id);
+#endif
+        }
+
+        // Reset pointer history.
+        averagingTouchFilter.historyStart[id] = 0;
+        averagingTouchFilter.historyEnd[id] = 0;
+        averagingTouchFilter.historyData[0].pointers[id].x = x;
+        averagingTouchFilter.historyData[0].pointers[id].y = y;
+        averagingTouchFilter.historyData[0].pointers[id].pressure = pressure;
+    }
+}
+
+bool InputDevice::TouchScreenState::isPointInsideDisplay(int32_t x, int32_t y) const {
+    if (! parameters.xAxis.valid || ! parameters.yAxis.valid) {
+        // Assume all points on a touch screen without valid axis parameters are
+        // inside the display.
+        return true;
+    }
+
+    return x >= parameters.xAxis.minValue
+        && x <= parameters.xAxis.maxValue
+        && y >= parameters.yAxis.minValue
+        && y <= parameters.yAxis.maxValue;
+}
+
+const InputDevice::VirtualKey* InputDevice::TouchScreenState::findVirtualKeyHit() const {
+    int32_t x = currentTouch.pointers[0].x;
+    int32_t y = currentTouch.pointers[0].y;
+    for (size_t i = 0; i < virtualKeys.size(); i++) {
+        const InputDevice::VirtualKey& virtualKey = virtualKeys[i];
+
+#if DEBUG_VIRTUAL_KEYS
+        LOGD("VirtualKeys: Hit test (%d, %d): keyCode=%d, scanCode=%d, "
+                "left=%d, top=%d, right=%d, bottom=%d",
+                x, y,
+                virtualKey.keyCode, virtualKey.scanCode,
+                virtualKey.hitLeft, virtualKey.hitTop,
+                virtualKey.hitRight, virtualKey.hitBottom);
+#endif
+
+        if (virtualKey.isHit(x, y)) {
+            return & virtualKey;
+        }
+    }
+
+    return NULL;
+}
+
+
+// --- InputDevice::SingleTouchScreenState ---
+
+void InputDevice::SingleTouchScreenState::reset() {
+    accumulator.clear();
+    current.down = false;
+    current.x = 0;
+    current.y = 0;
+    current.pressure = 0;
+    current.size = 0;
+}
+
+
+// --- InputDevice::MultiTouchScreenState ---
+
+void InputDevice::MultiTouchScreenState::reset() {
+    accumulator.clear();
+}
+
+} // namespace android